Ryuichi Miyano

DLC thin film preparation by cathodic arc deposition with a super droplet-free system

Abstract Diamond-like carbon films, which are fabricated by means of a cathodic vacuum arc with a graphite cathode, are investigated from the viewpoint of the number of macrodroplets on the film observed with an optical microscope. A straight-type filtered arc deposition (Linear-FAD) system, a 45° torus-type filtered arc deposition (Torus-FAD) system, and a newly developed T-shape filtered arc deposition (T-FAD) system were tested, comparing them with a normal cathodic arc deposition (normal-CAD) system and a shielded cathodic arc deposition (S-CAD) system. The three filtered arc deposition (FAD) type systems showed a remarkable reduction in graphite macrodroplets. Among the FADs, T-FAD drastically reduced the number of macrodroplets to 0.2–0.4% of that for normal-CAD and S-CAD, and to approximately 1% of that for Linear-FAD and Torus-FAD.

ZnO film formation using a steered and shielded reactive vacuum arc deposition

Abstract Zinc oxide (ZnO) thin films were prepared on a borosilicate glass substrate by a steered and shielded reactive vacuum arc deposition method. The cathode spot was driven on a cathode surface using weak and strong permanent magnets, placed behind the cathode. The radial magnetic flux densities at the bottom of cathode shoulder were 1.0 mT and 5.5 mT, respectively. The arc was operated at DC 30 A and the in-process pressure was varied from 0.1 to 5.0 Pa. No bias was applied to the substrate. The substrate temperature was below 75°C after 20-min deposition. The deposition rate increased with the in-process pressure until 1.0 Pa with both weak and strong magnets. X-Ray diffraction analysis revealed that all films had a strong ZnO (200) peak, indicating c-axis orientation. In particular, the films strongly oriented to (200) were obtained at 0.5–3.0 Pa for the strong magnet. Highly transparent films in visual region were obtained at 0.5 and 3.0 Pa with both weak and strong magnets. A refractive index at 600 nm varied from 1.75 to 1.95. With the strong magnet, electric resistivity varied from 10−3 to 15 Ω cm as the pressure increased. However, with the weak magnet, resistivity of the order of 10−3 Ω cm was obtained over a wide pressure range of 0.1–1.0 Pa.

Corrosion resistance of TiN coatings produced by various dry processes

The corrosion resistance of a TiN surface prepared by plasma-based ion implantation (PBII) was compared with that of TiN coating films prepared by sputtering deposition, plasma spraying, and shielded vacuum arc deposition. The corrosion test with the potentiodynamic polarization curve shows that the PBII sample had the best corrosion resistance. The SEM observation indicates that there was no pinhole on the TiN surface prepared by PBII. However, a lot of pinholes were observed in the TiN coating films prepared by the other dry coating processes.

Effect of substrate bias on AlN thin film preparation in shielded reactive vacuum arc deposition

Abstract Aluminum nitride (AlN) thin films were prepared using reactive cathodic vacuum arc deposition in conjunction with a macrodroplet shield plate. Various bias conditions, such as no bias (floating), 0-V bias (same potential as anode), DC bias of −10 to −30 V, and RF power of 25–200 W, were applied to the substrate table. For floating bias, a -axis-oriented film was obtained. For 0-V bias, the films prepared on molybdenum substrate showed no preferential orientation, although the film prepared on silicon and borosilicate glass showed a -axis-orientation. For RF bias, the orientation changed from the a - to the c -axis as the RF power increased. The hardest (27 GPa) film was obtained for 0-V bias, and the hardness of the other films ranged from 19 to 24 GPa. The refractive index of the film prepared on quartz substrate was approximately 2.0 over the visual and infrared regions for all films. The extinction coefficient was less than 0.01 over the visual and infrared regions, with the exception of the film prepared under the 0-V bias condition, which showed a higher value.

Amorphous Carbon Fibrilliform Nanomaterials Prepared by Chemical Vapor Deposition

Carbon nanomaterials were prepared by chemical vapor deposition (CVD) and hot-filament CVD (HF-CVD) methods. The substrates were silicon and copper plates on which catalytic metal or metal-oxide thin films were coated by means of the cathodic arc deposition technique. Ethylene gas was used as a precursor. HF-CVD with a filament temperature of 1,000°C yielded a larger amount of carbon deposit at a lower furnace temperature of 600°C. High-resolution microscopic observation revealed a variety of amorphous carbon nanomaterials, such as frost columns, coral beads, microcoils, nanocoils, and amorphous nanotubes.

Cathode spot motion in vacuum arc of zinc cathode under oxygen gas flow

Magnetically steered cathode spot(s) of a vacuum arc with a zinc (Zn) cathode was(were) observed using a high-speed video camera. The camera can take 4500 frames per second of 256/spl times/256 pixels. The transverse magnetic flux density for steering the cathode spot was 1.0 and 5.5 mT at the bottom of the cathode (64 mm in diameter) shoulder. The arc was operated at an arc current of dc 30 A and O/sub 2/ flow rate of 40 ml/min. The pressure was varied from 0.1 Pa to 5.0 Pa. The principal results obtained in the present study were as follows. The cathode spots were driven in the retrograde direction. When a strong magnet was used, the number of the cathode spots was smaller, the cathode spots revolved at the outer region of the cathode surface more of the time, and the velocity of the cathode spots was higher than when a weak magnet was used. The velocity of the cathode spots increased as the pressure increased.

Carbon nanotubes on electrodes in short-time heteroelectrode arc

Abstract Short-time arc discharges with a short gap were generated between heteroelectrodes in stationary and running arc mode, under 25 kP of He. The electrodes used were pure graphite (C), nickel and yttrium mixed graphite (C–Ni/Y), and molybdenum (Mo). After the arc discharge, the surfaces of the anode and cathode were microscopically observed. On Mo electrode surface, no nanotubes were observed. With regard to C electrode, the multiwall nanotubes were observed only at the cathode spot where the arc was forcibly extinguished, and no nanotubes were observed at the anode spot. On the other hand, when the C–Ni/Y was used for the electrode, the nanotubes were observed both at the cathode spot where the arc was forcibly extinguished, and at the anode spot. These nanotubes on C–Ni/Y electrode were of multiwall, not of single wall.

Influence of gap length and pressure on medium vacuum arc with Ti cathode in various ambient gases

Abstract Voltage, plasma potential and electron temperature of a medium vacuum arc ignited between Ti cathode and disk stainless steel anode were measured in various ambient gases; H 2 , N 2 , He and Ar. Gap length was varied from 75 to 450 mm. The result showed that the voltage increased with gap length and gas pressure, and that the voltages in H 2 and N 2 were higher than those in He and Ar. The influence of the gas species on the voltage was explained on the basis of: the mean free path; ionization and excitation processes of the gas; and ambipolar diffusion.

Production of High-Density Plasmas in Electron-Beam-Excited Plasma Device

We tried to enlarge the diameter of high-density beam plasmas in an electron-beam-excited plasma (EBEP) device. In order to enlarge the beam plasma, we made a cusp configuration at the end of the ion source region in the EBEP device. Also, a surface confined ring with permanent magnets called «surmac» was mounted on the cusp center to make the plasma profiles flat. It was found that high electron density (7×10 11 cm -3 ) and uniformity (ΔN e /N e <4% OVER 6 CMO) COULD BE OBTAINED AT LOW PRESSURE (7×10 -4 Torr)

Anode mode in cathodic arc deposition apparatus with various cathodes and ambient gases

The anode mode of a vacuum arc in a cathodic arc deposition apparatus was observed as a function of ambient gas pressure ranging from 0.01 to 300 Pa. The chamber (400 mm in diameter and 600 mm in length) made of stainless steel (SUS304) acted as the anode. The arc was operated at a relatively low constant current of 50 A. The cathode materials used were Al, Ti, Fe, Ni, and Cu, and ambient gases were He, Ne, Ar, H2, N2, O2, and CH4. The principal results are as follows. (1) As the pressure was increased, the anode mode changed from diffuse-arc to footpoint to plane luminous to anode-spot mode. (2) The anode mode and resultant arc voltage increase were strongly dependent on gas species, and weakly on the cathode material. (3) Comparing diatomic and polyatomic (H2, N2, O2, and CH4) with mono-atomic molecule gases (He, Ne, and Ar), the onset pressure of the anode mode transition in the former was lower, the arc voltage higher, and the footpoints more numerous, smaller, and clearer. Both the dependence of the ambient pressure and the influence of the cathode materials and gas species on the anode mode changes were explained by the ion deficiency theory.